Method of feeding water to boilers



R. M. OSTERMANN 'ET AL 3 METHOD OF FEEDING WATER To BOILERS Filed Dec. 17, 1931 INVENTORS udolfl iostermann and BY S d A.Shemdan ATTORNEY May 8, 1934.

& H kiw lOI Patented May 8, i334 PATENT @FFECE METHOD OF FEEDING WATER T BOILERS Rudolf M. Ostermann, Kenilworth, and Sidney A.

Sheridan, Chicago, Ill., assignors to The Superheater Company, New York, N. Y.

Application December 17, 1931, Serial No. 581,662

4 Claims.

Our invention relates to heater apparatus utilizing exhaust steam for preheating boiler feed water and aims to provide an apparatus adapt-ed to ope; te with a minimum of incrusta- 4 tion on the heater tubes and a method of operating such apparatus.

The use of indirect or closed type feed water heaters employing exhaust steam as the heating mediuzn has become common. The water fed thru such a heater often contains an appreciable amount of carbonates of lime, and rapid incrustaticn of the heater tubes then occurs at the temperatures to which the water is heated by the exhaust steam. Such incrustation seriously in- I terferes with the heat transfer and reduces the heater capacity.

It has been proposed in Patent #1311995, Alsberg, to introduce tannin or like colloids into feedwater before pumping the feedwater thru a I closed heater whose heat is supplied by exhaust steam from an engine and then into the boiler supplying such engine. Experience with the process or" Alsber s patent has shown that, when the usual prop on of tannin is added to the feedwater, it materially reduces the rate of formation of carbonate incrustation on the water side or" the tubes of the heater, but that the incrustation nevertheless develops in course of time when the feedwater is contaminated by calcium 1 carbonates.

It is an object of our invention to minimize the dimculty just mentioned.

Our invention is based on the observation that when the feedwater contains a colloid as well as calcium carbonates, the colloid is adsorbed on the incrustation so that the incrustation contains material quantities of colloid. In accordance with our invention, a colloid capable of reacting with incrustation oi the calcium carbonate type at boiler temperature to produce non-solid materials is mixed wi i the ieedwater prior to its passage into the feedwater heater and the feedwater hea er is heated to a temperature such as to cause a reaction between the colloid and the incipient incrustation on the water heating surface at times when the feeding of water to the boiler is interrupted. Preferably a colloid of the tannin type is used. The temperature attained by the heater tubes when supplied with exhaust steam or" approximately atmospheric pressure is not high enough to produce a sufiicient action between the tannin or like colloid and the calcium carbonate incrustation. The reaction between the tannin type colloids and the calcium carbonate incrustation produces at boiler temperatures a soluble salt or salts of calcium and carbonic acid gas, so that the water surface of the heater is washed comparatively clean when the feedwater is first again passed to the boiler.

The novel features of the invention are pointed out in the appended claims. The invention itself, however, together with its objects and advantages, will best be understood from a detail description of a feedwater heater embodying the apparatus features of the invention and adapted to operate in accordance with the process steps of our invention, and such a description will now be given in connection with the accompanying drawing in which Fig. 1 is an elevational view, parts being broken away, of a locomotive and its tender having an apparatus in accordance with our invention applied thereto.

Fig. 2 is a sectional view of an indirect or closed type feedwater heater shown in Fig. 1.

Referring to the drawing more in detail, is a boiler or" a locomotive having a tender 12 in which is a water tank 1% for storing I'eedwater for the boiler 10. A water supply line 15 connects the tank i l with the water cylinder 16 of a feedwater pump which forces the feedwater thru a line 18 to an indirect feedwater heater 20 and thence thru a pipe line 22 into the boiler 10. Tannin or like colloid is introduced into the feedwater prior to the introduction or" the ieedwater into the heater 20. Such introduction of the colloid can be accomplished very conveniently by having the locomotive fireman add the colloid to the water in tank 14 from time to time in a quantity proportionate to the amounts of fresh water taken into the tank. No special means, therefore, are required for adding the colloid to the feedwater and none are illustrated.

In the arrangement illustrated, the ordinary boiler check valve is shown at 24.. Ordinarily, the valve 24 prevents the hot fluid from boiler 10 from working back into the feedwater heater 20 thru the line 22. The tubes of heaters such as 20 therefor are not usually heated above 250 deg. F. because of using exhaust steam, altho the boiler tem erature usually is much higher, being 383 deg. F. when the boiler pressure is 260 lbs. In the arrangement shown, however, we have provided means including a by-pass 26 whereby the fluid in the boiler may be utilized to bring the tubes of the heater 20 up substantially to the boiler temperature during periods when no ieedwater is being forced into the boiler. 0i" course, when the feed pump is working, water passes to boiler 10 thru by-pass 26, as well as by the regular channel through the check valve 24. As shown, by-pass pipe 26 is taken out of the boiler 10 and connected into the line 22 on the heater side of the check valve 24 and preferably between check 24 and heater 20. By-pass 26 contains a valve 28 which may be adjusted by hand to regulate the amount of hot fluid which will pass from the boiler into the line 22. Preferably, valve 28 is adjusted so that hot fluid may pass from the boiler to the heater 20 at only a low rate, no large amount of fluid being necessary for the purpose in mind. Preferably, an additional check valve is placed on the pump side of the heater 20 as indicated at point 30. Such a check valve between the heater and the pump makes it possible to omit the bypass 26 in case check 24 is also omitted. In such case, the action is similar, although not as rapid as when by-pass 26 is used. However, it is preferred to use both the check valve 24 and the check valve 30 together with by-pass 26. In either case, the tubes of heater 20 will be cooled by the feedwater, whenever pump 16 is in operation, to such an extent that incipient incrustation of the tubes of the heater will occur in spite of the use of the usual amounts of tannin or the like in the feedwater. When, however, the flow of feedwater is interrupted from time to time, as is substantially always the case, the apparatus in accordance with our invention permits the hot fluid from the boiler to work back into the heater 20 and thereby raise the temperature of the tubes to such a point that chemical action occurs between the colloid and the incrustation to remove the incrustation in the manner previously indicated.

The line 26 can be connected below the water line 31 of boiler 10 or above it, as desired. How ever, it is desirable that the connection between lines 26 and 22 be above the water level as shown if steam is to be used as a heating medium. This j arrangement causes a natural thermal circulation in lines 26 and 22 so that the heater 20 may be rapidly brought to boiler temperature as soon as the operation of pump 16 has been interrupted. However, I do not limit myself to the arrangement illustrated. The operation of such arrangement in heating the feedwater heater 20 will be clear when it is considered that, when the feed pump 16 stops working, the pipe 22 stands full of water which is cooler and therefore heavier than the water within the boiler 10. The water in pipe 22, is, however, under the full boiler pressure owing to the connection 26. The hydrostatic pressure at the lower end of pipe 22 is therefore equal to the steam pressure plus the hydraulic head of the column of relatively cool water in the heater 20 and pipe 22. However, the hydrostatic pressure at the same level within boiler 10 is equal only to the steam pressure plus the hydraulic head of water from the water level 32 down to the lower end of pipe 22. The water in the pipe being cooler and therefore heavier, some of it flows thru the check valve 24 into the boiler thereby making room in the heater 20 for steam to enter thru the bypass 26 and thereby heat the inner surfaces of the water tubes within the heater 20 to the desired temperature.

Referring more particularly to Fig. 2, it will be seen that the particular feedwater heater 20 shown is of a known type having four groups of tubes 32, 34, 36 and 38. The pipe 18 delivers the water to the heater 20 at one end and it then flows thru tubes of group 32 to the other end, returning to the first end thru tubes of group 34. The water then makes two more passes, flowing away from the first end in tubes of group 36 and returning in tubes of 38. It will be seen that heating steam or hot boiler water from pipe 22 can readily pass back thru tubes of groups 38, 36 and 34. In the arrangement shown, the tubes of group 32 are nevertheless heated to considerable degree by convection within the shell of heater 20 and by conduction thru the shell.

It will be understood, therefore, that we do not limit ourselves to heating the entire heat transferring surfaces of the water heater to the reacting temperature.

While we have described a particular arrangement for heating the heater 20 during periods of interruption of the feed pump, we do not limit ourselves in all cases to such an arrangement or to the use of boiler fluid for this purpose. Further, we do not limit ourselves in all cases to tannin or to a colloid of the tannin type.

What we claim is:

1. The method of operating a feedwater heater of the closed type comprising adding to feedwater which may contain carbonates of lime a colloid capable of reacting with said carbonates at boiler temperature to form non-solid material, intermittently forcing the colloid-containing water to the boiler thru a closed feedwater heater, and heating at least some of the heat transferring surface of the heater at times when the flow of water therethru is interrupted to a temperature causing a reaction between any calcium incrustation on the heater and the colloid.

2. The method of operating a feedwater heater of the closed type comprising adding a colloid of the tannin type to boiler feedwater which may contain carbonates of lime, intermittently forcing said colloid-containing water to a boiler thru a closed heater, and heating at least some of the heat transferring surface of the heater at times when the flow of feedwater therethru is interrupted to a temperature promoting a chemical action between said colloid and any calcium containing incrustation on the surfaces of the heater to form soluble calcium material and carbonic acid gas.

3. The process as set forth in claim 1 and in which fluid from the boiler is utilized in heating the feedwater heater to the temperature desired for promoting reaction between the colloid and the incrustation.

4. The method of operating f edwater heaters of the closed type comprising utilizing exhaust steam as heating medium in a closed feedwater heater, adding to feedwater which may deposit calcium carbonate incrustation upon being heated a colloid which is adsorbed by calcium carbonate incrustation and which reacts with such incrustation at a temperature higher than that to which the heater normally raises the feedwater to produce non-solid products, and raising the temperature of the water touched surfaces of the heater to produce said reaction between the colloid and the incrustation at times when no feed-water is being forced thru the boiler.

RUDOLF M. OSTERMANN. SIDNEY A. SHERIDAN. 

